Raman spectroscopy is a photon scattering phenomenon. In this technique a laser is directed toward a test specimen and photon-molecule collisions are observed. The amount of energy transferred in the collision corresponds to the vibrational and rotational energy states of the target molecule bonds. The spectrum of observed scattered frequencies, known as the Raman spectrum, enables distinction of compounds containing the same atoms as long as they exist in different multiples or in different bond combinations. In general, the Raman line intensities relate to bonds in a molecule and will be consistent with molecule stoichiometry.
Recently interest has renewed in the identification and quantification of various oil compounds in common foods. It is known that the presence of unsaturated fatty acids such as oleic, linoleic and linolenic acid in food can help to lower total Low-Density Lipoprotein (LDL) cholesterol in the blood. Hence their presence in foods is encouraged, particularly as alternatives to saturated fats which are linked with obesity, heart diseases and their accompanying adverse effects in humans. Traditional means to detect these compounds are limited to methods such as gas chromatography/mass spectrometry (GC/MS) and NIR reflectance, but GC/MS analysis typically involves rather cumbersome sample gathering and preparation and NIR analysis tends to lack the sensitivity that the market may demand to differentiate substances containing minor variations in the target fatty acids. It is therefore believed that alternative analysis techniques may warrant pursuit. The work contained herein explores the use of an alternative method to identify and quantify these compounds which involves the use of time-resolved Raman spectroscopy. Further, this work is equally applicable to situations in which both the Raman and fluorescence information from a sample is to be gathered.